Underground liquid storage facility and the method of selecting and preparing the same



Nov. 1 7, 1953 R. v. PHELPs 2,659,209 UNDERGROUND LIQUID STORAGEFACILITY AND THE METHOD OF SELECTING AND PREPARING THE SAME Filed March25, 1951 Safz marly I saZe. aan q I 9 Sanaone.

l Zou-12s. Gmyzmy By l NOV. 17, 1953 R v PHELPS 2,659,209

UNDERGROUND LIQUID STORAGE FACILITY AND THE METHOD OF SELECTING ANDPREPARING THE SAME Filed March 23, 1951 5 Sheets-Sheet 2 Nov. 17, 1953 vPHELPs 2,659,209

"R. UNDERGROUND LIQUID STORAGE FACILITY AND THE METHOD OF SELECTING ANDPREPARING THE SAME Filed March 25, 1951 3 Sheets-Sheet 5 Ji' e z FJD/z605, 5y

mm1/4A 77K Patentecl Nov. 17, 1953 UNITED `STATES Rex Victor Phelps,Tulsa, Okla., assignor to Warren Petroleum Corporation, Tulsa, Okla., acorporation of Delaware Application March 23, 1951, Serial No. 217,211

13 Claims.

My invention consists in new`and useful im-V provements in undergroundliquid storage facili ties and the method of selecting and preparing thesame, and although it may be used for any liquid products, it has beenprimarily designed for use in connection with such products as liquiedpetroleum gas and the like.

It has been generally customary ,in the past to store liquifiedpetroleum gas in steel storage tanks and containers located above groundwhich has not only entailed considerable expense in construction andmaintenance, but has been attended by fire hazard and danger to.personnel and property because of exposed equipment. Furthermore, theshortage of steel from time to time has created a deniteproblemboth inconstruction and maintenance of above ground ster-- age equipment.

Although some efforts have been made to the end of underground storagefacilities, most of those with which I am familiar have not beenpractical because ofk the expense involved in lining underground cavernswith metal or concrete Walls, and the cost of the type of equipmentused.

It is therefore the object of the present invention to provideunderground liquid storage facilities designed to take advantage ofcertain geological formations inherent in the earth which renderunnecessary the lining of the storage cavern and make it possible tooperate the same with a f minimum of installation and maintenance costs.

Another object ofthe invention, is to provide underground liquid storage`facilities wherein the only equipment exposed above ground is the con,-trol dome, thereby. not only minimizing fire haaards but insuring to alarge extent against damopen'shaft drilled in a typical geologicalforma@ e tion suitable for use inV constructing my improved storagefacility. i A r Figure-2 is a similar view on an 'enlarged scale,showingthe casingandfconduits installed in the shaft.' f i Figure 3 is asectional view showing the above ground control dome.

Figure 4 is a sectional view taken online of Figure 3.

Figure 5 is a diagrammatic illustration of a vertical, longitudinalsection of a typical shaft and storage cavern.

Figures 6 to 8, inclusive, are illustrations of various wall profileswhich may be used for stor age caverns, and

Figure 9 isa diagrammatic illustration of.

method of providing a plurality of storage caverna L the storage ofliquid petroleum gas and I have found that a safeminimum depth is onefoot per pound'of pressure on the material to be stored. For example,for a pressure of 100 pounds (gauge) an excavation or storage cavityshould` be located at least 100 feet below ground. This may be varied tosome extent in cases where the roof formation is of `sufcientstrength toact as a conningmedium as well as an overburden, Such, Yfor example, assolid limestone or solid granite.

It is'also necessary that the storage cavity to bev excavated have aroof stratum consisting cf aformation which is impermeable, hard, andsubstantially free of fractures, and one having suflicient beam strengthto support the necessary overburden. An example of a suitable formationfor a roof structure would be massive limestone.

Of equal importance are the properties re quired for the walls of theexcavation which should also be impermeable, reasonably dry, devoid ofimpurities or properties which might have a deleterious effect upon theliquid stored. A suitable formation for the cavern walls would be tight,sandy, shale to shaly 'sandstone and silty grey shale.Y This formationis dry, nonwaterbearing, tight, andvwill not effect the storedmaterials.v f'

It is desirable, although not necessary, that the cavern formation befollowed immediately below by a hard formation suitable for a cavernrfloor, such,U for example, as hard brittle limeformation which islocated 100 feet below groundv is the hard, brittle limestonestratum I IIt Will be noted, however, that immediately 'followingI the stratum Ilis soft grey shale, sandstone, and soft flaky carbonaceous shale with astratum of hard -brittle limestone interposed. With the exfception ofthe intermediate layer of the lime-- stone, these strata arewaterbearing and the carbonaceous shale would have a deleterious electupon the product to be stored because of its sulphur content.

Thus, it will be seen that the rst succeeding suitable roofV structurewhich is: sufficiently deep to provide the necessary overburden and isin turn. succeeded by a sufcient depth of desirable formation for cavitywalls, is they stratum I2 of massive limestone. Following this stratumI2 is a relatively deep stratum composed of tight, sandy shale to Shalylimestone and silty grey shale, represented by the numeral I3, and thisis followed bya hard brittlelimestone stratum t4 well adapted to serveyas a cavern oor. The stratum I3, being of sufficient` depth andpossessing the necessary propertieais therefore-selected for thelocation of the cavern to be excavated.

The first step afterdrilling the open shaft i and locating Vthe positionfor the cavern, is to install a main casing IIS Ias will be seen fromFigure 2. This casing is of sufficient diameter to serve first as ameans of ingress and egress during the subsequent mining operation in excavating the cavern and, following this operation, is permitted toremainin. the shaft for connection to a. casingextension-lcA and tohouse the eduction'equipment as; will. hereinafter appear. Preferablythe'casing i5 'and its extension ld are approxi-mately 3Eiinehes ininside diameter.

The. main casing [5 islewered vtotheproner depth in thev shaft idpreferably about onefootbelowthe under-'face of thereof rock i2,.and issqueeze cemented from theA bottom of the.y roofl rockt tothe surface ofither ground. squeeze-cementing y is performed bythe usual oil heldpractice, thatv is, the shaft is filled with the proper quantity ofcement and water isithen forced through the casing to squeeze the cementout of the bottom of the casing 'and back'up'around Vthe outsidethereof, filling all' spaces and crevices' and tightly sealing theperiphery of the casing inthe shaft, from'theV roof rock t2 to theground surface, as shown at I5 inFigure 2. The cement is then allowed toset and :attain the Vrequired strength prior to testing the seal.

In order to test the seal so as to determine within a reasonable degreeof accuracy, whether or not an excavation will be successful, atemporary cap isplaced on the top of the casing' I5 and` a hydrostatictest is conducted on the formation and cement seal. This testisconducted by the Iual methods and need not be described in detail. YIfthe results of the test are satisfactory, the excavation of the caverncan be proceeded with. However, if there is any indication of leakage.around the cementvseal lr6, a. supplemental sealing structure,is-installed around the casing, adjacent the Vunder-side of the roofformation I2. This will be hereinafter referred to more in detail.

After the main casing I5 has been installed, sealed, and tested, theexcavation of the cavern is proceeded with and any modern miningpractices may be employed. At the commencement of` the mining operation,any excess cement or concrete at the bottom of the casing is drilled outand the shaft is continued in the stratum l 3 to the depth of the cavernto be excavated. A cavern I 'I ofthe desired size and shape is thencuthorizontally inY this stratum by the usual mining practices. Thiscavern I'I may take various Vshapes insofar as the profile of its Wallstructure-.is concerned, depending upon the nature of the formation ofthe stratum I3 and giving due considera-tion to the most economicalmethod of excavation. For example, if the substance of the cavern wallshas no tendency to Slough or cave in, the Walls can be substantiallyvertical asshown in profile in; Figure 6. On the outher hand, in astratum of denseshale or silty grey shale WhereV there is a likelihoodof' sloughing, the cavern is excavated with sloping sides to avoid thisfault'as shown in Figure 7. Figure 8 is simply another example of theprofile of the walls of a cavern, in this instance being substantiallycylindrical.

In Figure 5 I have illustrated a typical longitudinal cross section of astorage cavern which has been excavated horizontally from the bottom ofshaft ID and wherein an uncut mass IB is permitted to remain immediatelyadjacent the lower portion of the shaft I0, with an upper drift I9extending from the upper extremity of the cavern II to the shaft It. anda passage 25 extendingL horizontally from the lower portion of thecavern I'I to the bottom of the shaft III.

After the cavern I1 has` been excavated, an extension I5a is welded toYthelower end of the casing I5, as shown at. ZI in Figure 2. Thisextension may belowered intoathe shaft in sections or inv collapsed formand then welded in tubular shape. In its nal .form the extension I5c; isprovided with an entrance door or opening Zia. in its side wall, at thelower end of the extension, to afford access to the cavern from thecasing. Also a vapor opening 22 is cut in the wall of the extension IEagadjacent the upper drift I9, to admit vapo-r pressure into the spaceabout the level of the liquid to stored inthe cavern IV'I, as will.'hereinafter appear.

An eductor tube 23 is then installed inthe casing I5 and extends fromthe bottom ofv the extension 15a, to the ground level where itisconnectedthrough the wall of the casing to a liquid discharge conduit 24having a control valve 25 interposedV therein. The top of the casing I5is closed by a suitable control dome 26, welded to the.- upper end of;the casing I5. and having aremovably covered man hole 21 to permitentrance into the. casing. The bottom of the eductor tube 23 extends totheflower extremity of thefextension Ict and is preferably closed andsealed to a. steel plate 28 supported on a concrete base 29 whichsupports the bottom of ther extension 15a. One or more vertical slots 30arev cut in the wall-of the tube 23, a prede termined distance `aboveits lower end so as to provide for the admission of stored vliquid intolthe eductor tube, said slots being spaced upwardly from the bottom ofthe tube a sulicient distance to prevent the admission of water whichmay underlie the. stored liquid. Also extending vertically in the casingI5, is awater Siphon pipe 3|, the lower end of which terminates at thebottom of the extension in an angularly cut open end 32 so as to exposeits inlet opening in a plane below the slot 3i) in the eductor tube 23.Thus, water can be withdrawn through tube 3! without including oil inthe withdrawal. The

upper end of the water Siphon pipe 3I is connected through the wall ofthe casing I5 to a water drain conduit 33, as seen in Figure 4.

An air pressure conduit 34, leading from a suitable source of air orvapor pressure (not shown), is connected to the interior of the casingi5 through a sealed opening in its side wall as shown in Figures 3 and4, whereby airor vapor under pressure may be introduced into the casingI5 during the discharge of liquid from the cavern il. This vapor linealso serves the reverse funce tion of venting when the cavern is beingcharged with liquid to be stored.

In operation, the man hole cover 21 is first secured tightly in placeand when it is desired to discharge liquiiied petroleum gas orotherliquid stored in the cavern I'I, air or vapor under suitablepressure, is introduced through conduit 34 into the casing I5. By meansof the vapor opening 22 in the casing adjacent thev upper drift i9, thearea above the liquid level in the cavity is subjected to the pressurerequired to force the liquid upwardly through the eductor tube 23 andinto the discharge conduit 2li.

In storage facilities which are located at extreme depths, it may beadvantageous to utilize a pump for withdrawing the liquid from thecavern. However, in most instances, I have found that the use of vaporpressure on the upper surface of the stored liquid is sufficient toeffect a satisfactory discharge.

As before indicated, if the concrete seal I il satisfactorily withstandsthe hydrostatic test 1n the initial operations of installing thefacility, an additional sealing means is not necessary. However, in someinstances a supplemental sealing of the casing is required. Such meansis illustrated in Figure 2 of the drawings where f represents a atannular ring of suitable metal which is bolted into the roof structureI2 by means of expansion bolts 36 and surrounds the shaft openingradially beyond the concrete seal it. In installing the ring 35 thebottom surface of the limestone stratum i2 is ground to a polishedsealing t with the adjacent surface of the ring 35 so that when theexpansion bolts 38 are inserted, the ring 35 is maintained in sealingengagement with the under surface of the roof stratum I2. An annularbowl-shaped metallic head 3l surrounds the casing I5 immediately belowthe ring 35 and its upper edge is welded to the ring while its loweredge is welded to the casing extension Ilia. Thus, the pressure in thecavern has a self-sealing effect due to the structure of the head 31which has a tendency to force the ring 35 into even tighter sealingengagement with the roof stratum I2 so as to prevent leakage through theroof stratum i 2 past the casing I5.

In practice, both the ring 35 and the head 31 may be lowered into theshaft in sections of a size to pass through the casing l5, and thenwelded together prior to installation. It is believed unnecessary toillustrate this particular phase of the operation as it will be clearlyunderstood by those skilled in the art.

Facilities of this nature may be installed individually or a series ofcaverns may be arranged so as to utilize a common .unit of charg-V ingand discharging equipment. For example, invFigure 9 I have shown aseries of caverns I'I which'radiate from a common shaft ID which is usedboth inthe excavation of the caverns and for the installation ofcharging and discharging equipment. Obviously, many differentarrangements can be employed with equal effect, such, for example, as aseries of caverns arranged in parallel rows communicating with a commonshaft.

To facilitate the mining operation and to reduce costs, it may bedesirable to sink an auxiliary shaft of small diameter such, forexample, as 8 or 12 inches, to carry air, drilling tools, water, lights,or other utilities necessary for the operation. Normally this hole isplugged by cement after the excavation has been completed.

It will thus be seen that the use of my improved method and facilityenables the underground storage of large quantities of liquiliedpetroleum gas or the like under most economical conditions and with amaximum degree of safety. Furthermore, the vapor loading and unloadingsystem for withdrawing the liquid from the cavern is simple inconstruction and easyto install and operate. By the use of vaporpressure in discharging the liquid, I eliminate moisture from theproduct and the stored liquid can be with drawn at a greater rate perhour.

From the foregoing it is believed that my invention may be readilyunderstood by those skilled in the art without further description, itbeing borne in mind that numerous changes may be made in the detailsdisclosed, without departing from the spirit of the invention as setforth in the following claims.

I claim:

l. an underground storage facility for liquid under pressure, comprisinga vertical shaft ex-A tending into the ground, a subterranean. cavernhaving an overburden of a depth of at least one foot per pound gaugepressure on the liquid to be stored formed in the ground, extendingoutwardly from and connecting into said shaft, said shaft leading fromsaid cavern to grounr level, Va casing, closed at its upper end, liningsaid shaft and extending to the bottom of said cavern, an opening to thecavern, at the lower end of said casing, means sealing the casing insaid shaft, an eductor tube in said easing and having an inlet openingin its lower end, substantially at the botn tom of said casing, adischarge conduit connected to the upper end of said eductor tube, andmeans for discharging liquid from said cavern through said eductor tube.

2. An underground storage facility claimed in claim l, including meansfor introducing a gaseous pressure 4medium through said casing to thearea of said cavern above the liquid level therein, to displace liquidthrough said eductor tube.

3. An underground .storage facility as claimed in claim l, wherein saidcasing is of such transverse dimensions as to alford entrance and egresswith respect to the cavern and its lower end is provided with a cut outportion adapted to serve as an entrance doorway to the cavern.

s. An underground storage facility as claimed in claim 3, includingmeans for introducing a gaseous pressure medium through said casing tothe area of said cavern above the liquid level therein, to displace saidliquid through said eductor tube.

5. An underground storage facility as claimed infclaim, including asecond ropening in said lin a vplane above the level of the liquidstored in the cavern, and means for hitroducing argaseous pressure'medmmthrough said casing and second opening, ico the area above the liquidlevel in said cavern, @to displacesaid liquid through said feduotortube,

6.-An underground liquid :storage facility as claimed in claim l,wherein the inlet opening in said eductor -tu'be isspaced 'verticallyfrom the bottom of the cavern to prevent the entrance of Water whichmayunderliethe liquid stored in saidfcavern.

7. An underground liquid storage facility as claimed fclaim J6,including a Water Siphon tube extending from -the bottom .of said cavern-to ground level and having Aan inlet opening at .its lower end disposedin aplane below the plane of the inlet opening to said eductor tube.

8. An underground storage facility for liquids under pressure,.comprising a subterranean cavern having a relatively deep overburden,said cavern being bounded at its 4upper extremity .by a Ageological roofrock formation which is hard, impermeable, and substantially free from`raotunes, and having a thickness vand beam strength to support ltheWeight of said overburden, the :cavern being formed in a selected.stratum which is impermea le, substantially dry, and free fromproperties which would :aiect the `quality and consistenc-y -of theliquid stored therein a shaft leading from said cavern to ground level,a Vcasing cio'sed at i-ts upper end, lining said shaft, and opening intosai-d cavern in la plane above the level of the liquid stored therein,means .sealing the casing in said shaft, an -eductor tube eftencln ingthrough said casingand .having an inlet opening at its lower endsubstantially at the bottom of saidcavern, a discharge conduit connectedto the upper end .of said eductor tube, and means for dischargingPliquid from -said cavern through said `eductor tube.

9. In an underground storage facility as claimed in claim i8, asupplemental seal for said casing comprising av ilat annular ring insealing engagement with the under surface of said roof rock formationaround said shaft, means securing said ring to said roof rock formation,van annular, substantially `'bowl-.shaped head surrounding said casingbeneath said ring and sealed vrespectively at its upper and lowerextremities, to the under side of said ring Aand the periphery of .saidcasing.

l0. 1n underground storage facility as claimed in claim 8, asupplemental seal for said casing comprising a flat annular ringengaging the under surface of said roof rock formation around saidshazft, with a ground and polished nt, means securing said ring to saidroof rock formation, an annular, substantially bowl-shaped headsurrounding said casing beneath said ring and sealed respectively at itsupper and lower extremities, to the under :side of said ,ring and theperiphery of said casing.

11. In combination with a subterranean cavern having a vertical :shaftextending therefrom and a casing lining said shaft, means sealing saidcasing with Yrespect to ysaid shaft comprising a at annular platesurrounding said casing and in sealing engagement with the roof of thecavern, means securing said plate in sealing engagement, and an annular,substantially bowl-shaped head surrounding said casing beneath saidplate and sealed respectively at its upper and lower extremities, to theundersides of said plate and the periphery of said casing.

12. The method lof preparing an underground pressure :fluid storage`facility, comprising drilling a fcore 'to a geological formation havinga hard rock stratum possessing suitable roof properties and a depth toprovide a suicient overburden to retain pressure of the fluid to bestored, and immediately followed by a relatively deep second stratumwhich is dry, non-permeable by the iiuid to be stored, and devoid ofimpurities which will affect the huid to be stored, sinking a miningshaft along `the core bore, installing a casing in said shaft, sealingsaid casing with respect to the surrounding formation 'from the .bottomof the shaft to ground level, excavating an offset storage cavern in thesecond stratum from a point, adjocent the lower portion of said shaft,installing a liquid conducting discharge pipe through said casing fromground level 'to the bottom of the casing, and closing the top of Ysaidcasing.

13. The method as claimed in cla-im l2, including sealing Vthe casing byintroducing therein a quantity of cement in fluid state and then forcingWater under pressure, through said casing to squeeze said cement outthrough the lower end of the casing Iand up between the outer wall ofthe casing and the surrounding shaft,

REX VICTOR PEELPS.

References Cited in the le of this patent UNITED 'STATES PATENTS NumberName Date 2,433,896 Gay Jan. 6, 1948 2,459,227 'Kerr Jan. 18, 1949 OTHERREFERENCES Eng. News-Record, page '56, April 19, 1951.

